complex eigenvalues detected for tensor

thegauravonline · April 6, 2016, 08:10

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | foam-extend: Open Source CFD                    |
|  \\    /   O peration     | Version:     3.2                                |
|   \\  /    A nd           | Web:         http://www.foam-extend.org         |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1;

vertices
(
    (-5   0    -2.4)
    (0    0    -2.4)
    (0.04 0    -2.4)
    (10    0    -2.4)
    (-5   2.6  -2.4)
    (0    2.6  -2.4)
    (0.04 2.6  -2.4)
    (10    2.6  -2.4)
    (-5   2.8    -2.4)
    (0    2.8    -2.4)
    (0.04 2.8    -2.4)
    (10    2.8    -2.4)

    (-5   0     2.4)
    (0    0     2.4)
    (0.04 0     2.4)
    (10    0     2.4)
    (-5   2.6   2.4)
    (0    2.6   2.4)
    (0.04 2.6   2.4)
    (10    2.6   2.4)
    (-5   2.8     2.4)
    (0    2.8     2.4)
    (0.04 2.8     2.4)
    (10    2.8     2.4)
);

blocks
(
    hex (0 1 5 4 12 13 17 16) (40 20 10) simpleGrading (0.1 0.2 1)
    hex (2 3 7 6 14 15 19 18) (80 20 10) simpleGrading (10 0.2 1)
    hex (4 5 9 8 16 17 21 20) (40 20 10) simpleGrading (0.1 2 1)
    hex (5 6 10 9 17 18 22 21) (5 20 10) simpleGrading (1 2 1)
    hex (6 7 11 10 18 19 23 22) (80 20 10) simpleGrading (10 2 1)
);

edges
(
);

patches
(
    patch consoleFluid
    (
        (1 13 17 5)
        (5 17 18 6)
        (6 18 14 2)
    )
    wall topWall
    (
        (8 20 21 9)
        (9 21 22 10)
        (10 22 23 11)
    )
    wall bottomWall
    (
        (0 1 13 12)
        (2 3 15 14)
    )
    patch outlet
    (
        (3 7 19 15)
        (7 11 23 19)
    )
    wall inlet
    (
        (0 12 16 4)
        (4 16 20 8)
    )
    wall frontAndBackPlanes
    (
	(0 4 5 1)
	(4 8 9 5)
	(5 9 10 6)
	(2 6 7 3)
	(6 10 11 7)
	(12 13 17 16)
	(16 17 21 20)
	(17 18 22 21)
	(14 15 19 18)
	(18 19 23 22)
     )
);

mergePatchPairs
(
);

// ************************************************************************* //

This code runs fine for my geometry.

but when I change the convertToMeters 0.01 in the same blockMeshDict, i get an error after 6th iteration of first time step saying "complex eigenvalues detected for tensor"

Code:

Time = 0.01, iteration: 6
Current fsi under-relaxation factor (Aitken): 0.000591848
Maximal accumulated displacement of interface points: 0.0249799
DICPCG:  Solving for motionUx, Initial residual = 0.0630508, Final residual = 6.27685e-05, No Iterations 456
DICPCG:  Solving for motionUy, Initial residual = 0.320541, Final residual = 0.000320251, No Iterations 104
DICPCG:  Solving for motionUz, Initial residual = 0.199232, Final residual = 0.000198682, No Iterations 327
Courant Number mean: 0.258629 max: 27.4461 velocity magnitude: 0.391973
DILUPBiCG:  Solving for Ux, Initial residual = 0.705221, Final residual = 4.49245e-07, No Iterations 16
DILUPBiCG:  Solving for Uy, Initial residual = 0.900522, Final residual = 8.65619e-07, No Iterations 15
DILUPBiCG:  Solving for Uz, Initial residual = 0.628637, Final residual = 9.8274e-07, No Iterations 19
GAMG:  Solving for p, Initial residual = 0.963762, Final residual = 9.44056e-07, No Iterations 70
GAMG:  Solving for p, Initial residual = 3.71152e-07, Final residual = 3.1966e-07, No Iterations 1
time step continuity errors : sum local = 3.68598e-07, global = -8.70958e-10, cumulative = -8.63331e-10
GAMG:  Solving for p, Initial residual = 0.403809, Final residual = 9.54625e-07, No Iterations 60
GAMG:  Solving for p, Initial residual = 1.6799e-06, Final residual = 9.24074e-07, No Iterations 4
time step continuity errors : sum local = 5.16904e-07, global = 1.21874e-09, cumulative = 3.55412e-10
Setting traction on solid patch
Total traction force = (0.000978828 3.34429e-05 2.30297e-06)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (0.368474 -0.159926 0.561094 -0.0315612 -0.0259822 0 -1.56993 -1.03141 1)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (0.368474 -0.159926 0.561094 -0.0315612 -0.0259822 0 -1.56993 -1.03141 1)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (0.337311 -0.186135 0.565656 -0.072027 -0.142593 0 -1.60081 -1.05708 1)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (0.337311 -0.186135 0.565656 -0.072027 -0.142593 0 -1.60081 -1.05708 1)

What is going wrong with this?

tbao · October 10, 2016, 12:20

Quote:

Originally Posted by thegauravonline

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | foam-extend: Open Source CFD                    |
|  \\    /   O peration     | Version:     3.2                                |
|   \\  /    A nd           | Web:         http://www.foam-extend.org         |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1;

vertices
(
    (-5   0    -2.4)
    (0    0    -2.4)
    (0.04 0    -2.4)
    (10    0    -2.4)
    (-5   2.6  -2.4)
    (0    2.6  -2.4)
    (0.04 2.6  -2.4)
    (10    2.6  -2.4)
    (-5   2.8    -2.4)
    (0    2.8    -2.4)
    (0.04 2.8    -2.4)
    (10    2.8    -2.4)

    (-5   0     2.4)
    (0    0     2.4)
    (0.04 0     2.4)
    (10    0     2.4)
    (-5   2.6   2.4)
    (0    2.6   2.4)
    (0.04 2.6   2.4)
    (10    2.6   2.4)
    (-5   2.8     2.4)
    (0    2.8     2.4)
    (0.04 2.8     2.4)
    (10    2.8     2.4)
);

blocks
(
    hex (0 1 5 4 12 13 17 16) (40 20 10) simpleGrading (0.1 0.2 1)
    hex (2 3 7 6 14 15 19 18) (80 20 10) simpleGrading (10 0.2 1)
    hex (4 5 9 8 16 17 21 20) (40 20 10) simpleGrading (0.1 2 1)
    hex (5 6 10 9 17 18 22 21) (5 20 10) simpleGrading (1 2 1)
    hex (6 7 11 10 18 19 23 22) (80 20 10) simpleGrading (10 2 1)
);

edges
(
);

patches
(
    patch consoleFluid
    (
        (1 13 17 5)
        (5 17 18 6)
        (6 18 14 2)
    )
    wall topWall
    (
        (8 20 21 9)
        (9 21 22 10)
        (10 22 23 11)
    )
    wall bottomWall
    (
        (0 1 13 12)
        (2 3 15 14)
    )
    patch outlet
    (
        (3 7 19 15)
        (7 11 23 19)
    )
    wall inlet
    (
        (0 12 16 4)
        (4 16 20 8)
    )
    wall frontAndBackPlanes
    (
	(0 4 5 1)
	(4 8 9 5)
	(5 9 10 6)
	(2 6 7 3)
	(6 10 11 7)
	(12 13 17 16)
	(16 17 21 20)
	(17 18 22 21)
	(14 15 19 18)
	(18 19 23 22)
     )
);

mergePatchPairs
(
);

// ************************************************************************* //

This code runs fine for my geometry.

but when I change the convertToMeters 0.01 in the same blockMeshDict, i get an error after 6th iteration of first time step saying "complex eigenvalues detected for tensor"

Code:

Time = 0.01, iteration: 6
Current fsi under-relaxation factor (Aitken): 0.000591848
Maximal accumulated displacement of interface points: 0.0249799
DICPCG:  Solving for motionUx, Initial residual = 0.0630508, Final residual = 6.27685e-05, No Iterations 456
DICPCG:  Solving for motionUy, Initial residual = 0.320541, Final residual = 0.000320251, No Iterations 104
DICPCG:  Solving for motionUz, Initial residual = 0.199232, Final residual = 0.000198682, No Iterations 327
Courant Number mean: 0.258629 max: 27.4461 velocity magnitude: 0.391973
DILUPBiCG:  Solving for Ux, Initial residual = 0.705221, Final residual = 4.49245e-07, No Iterations 16
DILUPBiCG:  Solving for Uy, Initial residual = 0.900522, Final residual = 8.65619e-07, No Iterations 15
DILUPBiCG:  Solving for Uz, Initial residual = 0.628637, Final residual = 9.8274e-07, No Iterations 19
GAMG:  Solving for p, Initial residual = 0.963762, Final residual = 9.44056e-07, No Iterations 70
GAMG:  Solving for p, Initial residual = 3.71152e-07, Final residual = 3.1966e-07, No Iterations 1
time step continuity errors : sum local = 3.68598e-07, global = -8.70958e-10, cumulative = -8.63331e-10
GAMG:  Solving for p, Initial residual = 0.403809, Final residual = 9.54625e-07, No Iterations 60
GAMG:  Solving for p, Initial residual = 1.6799e-06, Final residual = 9.24074e-07, No Iterations 4
time step continuity errors : sum local = 5.16904e-07, global = 1.21874e-09, cumulative = 3.55412e-10
Setting traction on solid patch
Total traction force = (0.000978828 3.34429e-05 2.30297e-06)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (0.368474 -0.159926 0.561094 -0.0315612 -0.0259822 0 -1.56993 -1.03141 1)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (0.368474 -0.159926 0.561094 -0.0315612 -0.0259822 0 -1.56993 -1.03141 1)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (0.337311 -0.186135 0.565656 -0.072027 -0.142593 0 -1.60081 -1.05708 1)
--> FOAM Warning : 
    From function eigenValues(const tensor&)
    in file primitives/Tensor/tensor/tensor.C at line 170
    complex eigenvalues detected for tensor: (0.337311 -0.186135 0.565656 -0.072027 -0.142593 0 -1.60081 -1.05708 1)

What is going wrong with this?

Hi,

Did you solve this problem? I met the same problem but have not solved yet. Any hit is appreciated.

KarthickRajkumar · January 10, 2017, 16:23

Quote:

Originally Posted by tbao

Hi,

Did you solve this problem? I met the same problem but have not solved yet. Any hit is appreciated.

I am doing implementation of compressible flow solver in FSI library in foam -extend 3.2, where I face this similar problem!

Did you fix it? If so, could you please share how did you do it!

Thanks,
Karthick

thegauravonline · January 14, 2017, 06:18

Yes I did solve it. But I just cant remember what the problem was.

I think it was something due to inappropriate material properties.

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January 14, 2017, 06:18		#4
thegauravonline Member GS Join Date: Mar 2016 Posts: 81 Rep Power: 10	Yes I did solve it. But I just cant remember what the problem was. I think it was something due to inappropriate material properties.